1. Field of the Invention
The present invention relates to a digital-broadcasting receiving apparatus and a digital-broadcasting receiving method.
2. Description of Related Art
A digital-broadcasting wave includes a broadcast data of a physical channel assigned to each frequency band area, and the broadcast data of each physical channel includes a broadcast data of plural sub-channels. In order to allow the broadcast data of the physical channel assigned to the limited frequency band area to include the broadcast data of plural sub-channels, a video data, an audio data, etc., which are included in the broadcast data of the physical channel are coded and multiplexed by the MPEG2 (Moving Picture Experts Group Phase2)-TS (Transport Stream) system. Therefore, in order to view the broadcast data of each sub-channel, in the digital broadcasting receiving apparatus which receives a digital-broadcasting airwave, it is necessary to recognize and register individually beforehand the sub-channel included in the digital-broadcasting wave. Then, the technique to scan and register the broadcast data of the sub-channel included in the digital-broadcasting wave has been developed (e.g. JP2002-101353A).
The sub-channel includes a free sub-channel and a pay sub-channel. A video data, a audio data, etc. of the pay sub-channel are usually coded (hereinafter referred to as “scrambled”) so that only the person who paid a charge can view it. In some cases, the non-scrambled broadcast data of the sub-channel and the scrambled broadcast data of the sub-channel are mixed in the broadcast data of the physical channel. In this case, when all the broadcast data of the sub-channels included in the digital-broadcasting wave are scanned and registered, non-scrambled sub-channels which are not viewable are also registered.
The technique to judge, by referring to a tsc (transport scrambling control) bit included in a header region of the broadcast data of the sub-channel which is coded and multiplexed by the MPEG2-TS system included in the broadcast wave, whether the broadcast data of the sub-channel is scrambled or not is known (JPHei11-220655A).
However, actually, because the tsc bit does not often reflect whether the broadcast data is scrambled or not, there is the case that it cannot be exactly judged whether it is scrambled or not by referring the tsc bit. It is possible, by actually decoding the video data and judging whether it can be decoded or not, to judge exactly whether it is scrambled or not. However, because it takes time to decode the scrambled video data, it is not realistic to scan all frequency bands area including the broadcast data of all sub-channels while examining whether they can be decoded or not.